day 2 done

day2/main.go

@@ -0,0 +1,177 @@
+package main
+
+import (
+	"bufio"
+	"fmt"
+	"os"
+	"strings"
+)
+
+func main() {
+	if len(os.Args) < 2 {
+		panic("Provide input file")
+	}
+	inputFile := os.Args[1]
+
+	part1 := part1(inputFile)
+	fmt.Printf("(%s) Part 1: %d\n", inputFile, part1)
+
+	part2 := part2(inputFile)
+	fmt.Printf("(%s) Part 2: %d\n", inputFile, part2)
+}
+
+func part2(inputFile string) int {
+	input, err := os.Open(inputFile)
+	if err != nil {
+		panic(err)
+	}
+	defer input.Close()
+
+	var rawReports []string
+
+	scanner := bufio.NewScanner(input)
+	for scanner.Scan() {
+		rawReports = append(rawReports, scanner.Text())
+	}
+
+	safeReports := 0
+	for _, report := range rawReports {
+		if safe2(report) {
+			safeReports++
+		}
+	}
+
+	return safeReports
+}
+
+func safe2(line string) bool {
+	var safe bool
+
+	levels := strings.Split(line, " ")
+	levelInts := make([]int, len(levels))
+	for i, level := range levels {
+		fmt.Sscanf(level, "%d", &levelInts[i])
+	}
+
+	// now we can remove any one level and check if it passes the 1-3 increasing or decreasing check
+	dampener := -1
+	combinations := len(levelInts) + 1
+
+	for i := 0; i < combinations; i++ {
+		testArray := make([]int, 0)
+		if dampener > -1 { // we can try skipping a level
+			for j := 0; j < len(levelInts); j++ {
+				if j != dampener {
+					testArray = append(testArray, levelInts[j])
+				}
+			}
+		} else { // try the original levels no skipping
+			for j := 0; j < len(levelInts); j++ {
+				testArray = append(testArray, levelInts[j])
+			}
+		}
+
+		var increasing bool
+		if testArray[1] > testArray[0] {
+			increasing = true
+		} else {
+			increasing = false
+		}
+
+		for i := 1; i < len(testArray); i++ {
+			if increasing {
+				if testArray[i]-testArray[i-1] > 3 || testArray[i]-testArray[i-1] < 1 {
+					safe = false
+					break
+				}
+				if testArray[i] < testArray[i-1] {
+					safe = false
+					break
+				}
+				safe = true
+			} else {
+				if testArray[i-1]-testArray[i] > 3 || testArray[i-1]-testArray[i] < 1 {
+					safe = false
+					break
+				}
+				if testArray[i-1] < testArray[i] {
+					safe = false
+					break
+				}
+				safe = true
+			}
+		}
+
+		if safe { // if we find a safe report we can return
+			return safe
+		} else { // if not we can try skipping levels using the dampener
+			dampener++
+		}
+	}
+
+	return safe
+}
+
+func part1(inputFile string) int {
+	input, err := os.Open(inputFile)
+	if err != nil {
+		panic(err)
+	}
+	defer input.Close()
+
+	var rawReports []string
+
+	scanner := bufio.NewScanner(input)
+	for scanner.Scan() {
+		rawReports = append(rawReports, scanner.Text())
+	}
+
+	safeReports := 0
+	for _, report := range rawReports {
+		if safe(report) {
+			safeReports++
+		}
+	}
+
+	return safeReports
+}
+
+func safe(line string) bool {
+	// safe if all adjacent numbers differ by 1-3 (inclusive)
+
+	levels := strings.Split(line, " ")
+	levelInts := make([]int, len(levels))
+	for i, level := range levels {
+		fmt.Sscanf(level, "%d", &levelInts[i])
+	}
+
+	var increasing bool
+	if levelInts[1] > levelInts[0] {
+		increasing = true
+	} else {
+		increasing = false
+	}
+
+	if increasing {
+		for i := 1; i < len(levelInts); i++ {
+			if levelInts[i]-levelInts[i-1] > 3 || levelInts[i]-levelInts[i-1] < 1 {
+				return false
+			}
+
+			if levelInts[i] < levelInts[i-1] {
+				return false
+			}
+		}
+		return true
+	} else {
+		for i := 1; i < len(levelInts); i++ {
+			if levelInts[i-1]-levelInts[i] > 3 || levelInts[i-1]-levelInts[i] < 1 {
+				return false
+			}
+			if levelInts[i-1] < levelInts[i] {
+				return false
+			}
+		}
+		return true
+	}
+}

day2/run

@@ -0,0 +1,4 @@
+#!/bin/bash
+
+go build -o ./bin/solution ./main.go
+./bin/solution "$1"